(1) Field of the Invention
The present invention generally relates to a cylinder head of an internal combustion engine, and more particularly to a cylinder head in which an intake valve and/or an exhaust valve of an internal combustion engine is operated by a solenoid valve control device.
(2) Description of the Related Art
Japanese Laid-Open Patent Application No. 7-305612 discloses a solenoid valve control device which electromagnetically operates an intake valve or an exhaust valve of an internal combustion engine.
The solenoid valve control device of the above-mentioned publication includes a valve element which serves as the intake valve or the exhaust valve of the engine. An armature of a magnetic material is connected to the valve element. In the solenoid valve control device, a first solenoid is provided above the armature and a second solenoid is provided below the armature. The solenoid valve control device controls one of the first solenoid and the second solenoid to generate an electromagnetic force such that the valve element is operated to open or close the intake valve or the exhaust valve of the engine.
In the conventional device of the above-mentioned publication, the valve element is accommodated in a cylinder head, and the first solenoid, the second solenoid, the armature and others are accommodated in an upper housing on the top of the cylinder head. However, the above-mentioned publication does not disclose a specific method of mounting the first solenoid, the second solenoid and the armature in the upper housing. The above-mentioned publication does not disclose specific, appropriate, relative positions of the first and second solenoids and the armature.
In the conventional device of the above-mentioned publication, the first solenoid and the second solenoid are completely supported by cylindrical members (which are provided in the upper housing) such that the relative positions of the first solenoid and the second solenoid to the armature are kept at appropriate positions. Since the cylindrical members are used in the conventional device, the outer diameters of the first solenoid and the second solenoid are required to be smaller than the inner diameters of the cylindrical members. Also, the outer diameter of the armature is required to be smaller than the inner diameters of the cylindrical members. In the conventional device of the above-mentioned publication, it is difficult to provide a large diameter for each of the first solenoid, the second solenoid and the armature because of the use of the cylindrical members.
Generally, a solenoid valve control device including a solenoid having a large diameter and an armature having a large diameter is required in order to exert a large electromagnetic force on the intake valve or the exhaust valve of the engine. However, the solenoid valve control device of the above-mentioned publication fails to provide an adequate structure to exert a large electromagnetic force on the intake valve or the exhaust valve of the engine.
Further, in the conventional device of the above-mentioned publication, the first solenoid and the second solenoid are completely supported by the cylindrical members in the upper housing, and an outer periphery of the first solenoid and an outer periphery of the second solenoid come into contact with the cylindrical member. It is difficult for the solenoid valve control device of the above-mentioned publication to bring the outer periphery of the first solenoid and the outer periphery of the second solenoid into contact with the upper housing.
During operation of the engine, heat is generated by the first solenoid and the second solenoid in the solenoid valve control device. It is desirable that a cylinder head having a solenoid valve control device provided therein effectively dissipates the heat from the first solenoid and the heat from the second solenoid. The larger the contact area of the first and second solenoids and the upper housing (or another member), the more effective the heat dissipation is. However, the solenoid valve control device of the above-mentioned publication fails to provide effective heat dissipation for a cylinder head having a solenoid valve control device provided therein.